This invention relates to a method and apparatus for producing foamable compositions and a method for making the same. More particularly, the invention relates to such a foamable composition which, when mixed with suitable amounts of air and water, produces a compressed air foam which is sufficiently stable to be used as an effective daily cover for landfills. The invention also relates to an apparatus designed to produce a compressed air foam from the foamable composition.
The invention further relates to a method and apparatus for mixing different materials for producing compositions other than foamable compositions.
Pursuant to federal, state and local laws, municipal solid waste (MSW) landfills are required to be covered by an earthen or other approved cover for wastes deposited therein at the close of each working day. The use of earthen material as a cover imposes two significant costs on the landfill operator. First, the material must be purchased and, even when available on site, must be physically transported to the landfill and then spread evenly over the compacted trash. The transporting of the earthen material requires large and expensive earth moving equipment as well as substantial man power. Secondly, the earthen material takes up valuable volume which could otherwise be sold to customers. More specifically, the use of earthen material can consume as much as 15 to 20 percent of landfill volume. This deprives the landfill operator of significant potential revenue and profit. Further, the landfill capacity wasted by the earthen material reduces the useful life of the facility, thereby resulting in the need for landfills of increased size or the development of new sites.
Accordingly, there is a need for a material which can be used to effectively cover a landfill without requiring expensive purchase and/or transportation costs. Further, there is a need for such a material which does not consume substantial amounts of valuable landfill volume. Such a material would significantly reduce the operating costs for the approximately 3000 landfills in the United States alone as well as the thousands of landfills abroad.
In recognition of the foregoing, a number of states have allowed foams to be used as covers if they meet certain statutorily provided requirements. For example, the covers must prevent the emission of certain volatile organic compounds and odors. The covers must also prevent the dispersal of loose trash at the landfill site and its vicinity. Foams replace the aggregate material in earthen materials with air. Thus, the use of foams as covers for landfills in place of the earthen material is desirable in that the foams do not take up as much volume as the earthen material and, therefore, are of economic value to the landfill operator. Moreover, such foams are typically less costly and easier to apply than other alternative daily cover methods or products.
Various air foam compositions have been in use for fire fighting purposes for many years. Examples of such foam compositions are disclosed in U.S. Pat. Nos. 3,849,315, 4,099,574, 4,594,167, 5,207,932, and 5,225,094. Three prevalent fire fighting foam compositions comprise either partially hydrolyzed protein, detergents or film forming foam compositions based on perfluorinated hydrocarbons. The detergent foams are generally used as high expansion systems for rapidly flooding large spaces in order to extinguish fires in warehouses, hangers or the like. The perfluorinated hydrocarbon based foams, known as aqueous film forming foams (AFFF), are useful for rapidly spreading an extinguishing film over a burning liquid. Protein based air foam systems provide stable extinguishing foams of relatively greater stability and a practical expansion factor of 10 when used in a 3 or 6% by volume solution of the foam producing composition in conjunction with typical foam generating apparatus.
None of the existing foam systems mentioned above can be used effectively as a daily cover for municipal solid waste (MSW) landfills. More specifically, such foam systems do not remain stable for the period between the day""s end of disposal operations and the beginning of the operations the following day. Further, such existing foam systems have expansion factors which are not adequate for use on landfills.
An additional problem with existing foam systems is that the apparatus utilized to discharge the foam fail to provide a sufficiently reliable discharge pattern or distance, thereby necessitating the use of costly additional equipment.
Air foams, protein or film forming types, produced with aspirating discharge nozzles, as are common in the fire protection industry, generally have an expansion factor of 10. This is the case with both 3 and 6% by volume solutions. The injection of compressed air into the foam solution instead of drawing air in by way of aspirating nozzles has been seen to raise the expansion factor to about 15. In most systems that utilize compressed air injection, the foam thus created is forced by pressure through a series of screens within a chamber. As the foam is passed through these screens, bubbles in the foam are reduced in size. A drawback with this process is that some of the fragile foam bubbles are destroyed as they pass through the screens. This reduces the amount of foam produced and, therefore, the expansion factor.
An additional drawback with the process described above is that the velocity of the foam as it is discharged is reduced as it passes through the systems due to contact with the series of screens. This results in a tube like stream of foam being created. When this tube like stream is discharged into the air, the tube like shape is maintain, thereby limiting the foam""s exposure to air. The limited air exposure has an adverse impact on the expansion factor of the foam.
The present invention is designed to overcome the deficiencies of the prior art discussed above. It is an object of the present invention to provide a foamable protein composition which, when mixed with suitable amounts of air and water, produces a foam which remains stable for an extended period of time.
It is a further object of the invention to provide such a foamable composition which is relatively inexpensive to manufacture.
It is still another object of the invention to provide a method and apparatus for producing an air foam from the foamable composition.
In accordance with the illustrative embodiments, demonstrating features and advantages of the present invention, there is provided a foamable composition which comprises a metal based salt and a hydrolyzed protein. The foamable composition, when mixed with suitable amounts of air and water, produces a foam which is stable for at least about 16 hours and, preferably, for at least about 18 hours and, more preferably, for at least about 24 hours.
Accordingly, the foam provides an effective daily cover for landfills and the like. Further, the foam can be utilized to provide a cover for hazardous and other wastes while such materials are in transit. It can also be used for fire fighting applications where extended stability is required, such as with forest or tire fires. Other applications include utilizing the foam to: insulate freshly poured concrete or agricultural crops; reduce or eliminate odor and other emissions from agricultural waste, apply fertilizer to the leaves of plants.
This invention also provides an apparatus for generating the protein foam from the foamable composition. The apparatus includes an injection chamber, an expansion chamber and at least one coiled hose which extends therebetween. The coiled hose includes a plurality of turns. Pressure generating pumps are provided to draw the foamable composition, which is preferably in liquid form, and water in a proper proportion and force a stream of the resulting foamable solution into the injection chamber where it is mixed with a pressurized stream of air and passed through the injection chamber, through the coiled hose, through the expansion chamber, through a length of hose and finally out a discharge nozzle in order to yield the desired air foam.
The invention further provides a method of preparing the foamable composition described above.
Additionally, the invention defined in the instant claims is also directed to a novel method and apparatus that is useful for mixing different materials to produce compositions other than foamable compositions.